The cross-referenced issued patent discloses various embodiments of a load-bearing air cushion device in which an annular sealing assembly for confining an air cushion comprises an annular hanger which inflates downwardly from a load-bearing base together with a flexible resiliently yieldable annular sealing means which projects downward from the annular hanger into close proximity to the ground or support surface along which the vehicle travels.
In the application of this technology to the design of practical air cushion vehicles, it was found that certain combinations of design parameters are critical and must fall within well defined ranges to avoid dynamic instability of the loaded vehicle. Also it was found that operational advantages accrue from separately inflating the seal hanger and the lifting cushion. However, the ratio of pressures in these two components must fall within defined limits. If the inflation pressure in the seal hanger is too low compared to pressure in the lifting cushion, the hanger will tend to collapse allowing the loaded vehicle to settle to the floor. On the other hand, if the hanger inflation pressure is too high the vehicle will experience dynamic instability which increases in severity as this pressure is increased.
It is a primary objective of this invention to define and claim the useful working ranges of critical design parameters required to avoid dynamic instability of this type air cushion vehicle. Structure is also described and claimed which prevents inadvertant over-pressurization of the seal hanger at all loads carried by the air cushion vehicle.
Another objective of this invention is to provide a sealing assembly comprising an annular inflatable hanger with an annular sealing means dependent therefrom in which the annular sealing means is made of relatively soft resiliently deformable material of substantial vertical dimension and yet does not expand outward radially under pressure inside the confined air cushion even when this pressure is substantially greater than pressures attained with previous designs.